Identification of molecules based on frequency responses using electromagnetic write-heads and magneto-resistive sensors

ABSTRACT

The invention relates to the identification of molecules using an apparatus which includes: a head module comprising: an electromagnetic write-head configured to magnetically excite the molecule to be identified with an alternating magnetic field; and a magneto-resistive read sensor for measuring a resonant response of the magnetically excited molecule to be identified. The apparatus also includes a processor coupled to the magneto-resistive sensor, the processor being configured to compare the resonant response to a table of known resonant responses to identify a chemical composition of the molecule to be identified.

BACKGROUND

The present invention relates to analytical devices and processes, andmore particularly, to devices and processes that incorporateelectromagnetic write-heads and magneto-resistive read-sensors toidentify the chemical composition of molecules based on the frequencyresponses of magnetically excited molecules.

Microchip sensors are incorporated into bio-assay devices and systems todetect the presence of viruses, cancer proteins, and other biologicalsubstances of interest. The microchip sensors may be in the form ofsilicon chip arrays and contain thousands of sensors, each coated with adifferent antibody that would latch on a particular virus or protein,and thus indicating the presence of target viruses or proteins and theirconcentration in a biological sample.

It is desirable to exploit the use of magnetic signaling technology toautomate the identification of molecules, such as viruses and cancerproteins, and to further apply this technology to the detection of anybiological matter.

BRIEF SUMMARY

Exemplary embodiments of the invention relate to analytical devices andprocesses. More particularly, the embodiments provide an apparatus,method, and computer program product that use electromagneticwrite-heads and magneto-resistive read-sensors to identify the chemicalcomposition of molecules based on the frequency responses ofmagnetically excited molecules.

In an exemplary embodiment of the invention, an apparatus foridentifying a molecule is disclosed. The apparatus includes a headmodule comprising: an electromagnetic write-head configured tomagnetically excite the molecule to be identified with an alternatingmagnetic field; and a magneto-resistive read sensor for measuring aresonant response of the magnetically excited molecule to be identified.The apparatus also includes a processor coupled to the magneto-resistivesensor, the processor being configured to compare the resonant responseto a table of known resonant responses to identify a chemicalcomposition of the molecule to be identified.

In another exemplary embodiment, a method for identifying a molecule isdisclosed. The method comprises magnetically exciting the molecule withan alternating magnetic field generated by an electromagneticwrite-head, measuring a resonant response of the molecule with amagneto-resistive sensor, and comparing the resonant response to a tableof known responses to identify the chemical composition of the molecule.

In a further embodiment, a computer program product for identifying amolecule is disclosed. The computer program product comprises a computerreadable storage medium having computer readable program code embodiedtherewith. The computer readable program code is configured tomagnetically excite the molecule with an alternating magnetic fieldgenerated by an electromagnetic write-head, measure a resonant responseof the molecule with a magneto-resistive sensor, and compare theresonant response to a table of known responses to identify the chemicalcomposition of the molecule.

For a fuller understanding of the invention, reference is made to thefollowing detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a top view of an exemplary substrate that includesbiosample tracks for carrying biosample molecules that may be scannedand identified by the embodiments of the invention.

FIG. 2 is a block diagram of an exemplary Z-pattern servo-alignment markfor aligning an electromagnetic read-write head with a biosample track,in accordance with an embodiment of the invention.

FIG. 3 is a block diagram of a side view of an exemplary biosample trackrelative to an electromagnetic read-write head for analyzing andidentifying molecules in a biosample, in accordance with an embodimentof the invention.

FIG. 4A illustrates a block diagram of a system for identifying amolecule using an electromagnetic read-write head, in accordance with anembodiment of the invention.

FIG. 4B illustrates an example of a glucose molecule being encapsulatedin a carbon nanotube, in accordance with an embodiment of the invention.

FIG. 5 is a block diagram of an exemplary circuit for controlling theX-axis and Y-axis motion of the read-write head-module of an analyticaldevice, in accordance with an embodiment of the invention.

FIG. 6 is a block diagram of an exemplary write and read circuit for usewith an analytical device, in accordance with an embodiment of theinvention.

FIG. 7 is a flowchart illustrating an exemplary process for identifyinga molecule using an electromagnetic read-write head, in accordance withan embodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the invention relate to methods and systems foridentifying molecules in biosamples using electromagnetic thin-filmwrite-heads and magneto-resistance read-sensors. The invention isdescribed in exemplary embodiments with reference to the Figures, inwhich like numbers represent the same or similar elements. It will beappreciated by those skilled in the art that variations may beaccomplished in view of these teachings without deviating from thespirit or scope of the invention.

Referring to FIG. 1, there is illustrated a top view of an examplesubstrate 101, which may comprise a Peltier™ hard-substrate, a glasssubstrate, a polyethylene terephthalate (PET, which is commonly known bythe trade name of Mylar™) flexible-substrate, or other materials havingsimilar properties. In an exemplary embodiment of the invention,head-module 105 scans across stationary substrate 101 fromleft-to-right, along the +Y-axis, individually sampling one orsimultaneously sampling a plurality of biosample tracks 102.Alternatively, substrate 101 may be swept across stationary head-module105 from right-to-left, along the −Y-axis. If substrate 101 is of aflexible polyethylene terephthalate material, then in one embodiment,this right-to-left motion may be performed as data read-write operationsin a magnetic tape drive. As an alternate embodiment of the invention,head-module 105 comprises a helical-scan rotary head-module, and theY-axis of the biosample tracks 102 is at an angle to the substrate.

FIG. 1 shows electromagnetic write-heads 107 and magneto-resistiveread-sensors 106 arranged in pairs in head-module 105. In oneembodiment, write-heads 107 and read-sensors 106 are on the samehead-module 105. In an alternate embodiment, write-heads 107 andread-sensors 106 may be independently adjustable. In yet anotherembodiment, a write-head 107 and a read-sensor 106 in a pair may beorthogonal to one another so that the magnetic excitation signal ofwrite-head 107 is less dominant to read-sensor 106. The electromagneticwrite-heads 107 first write to biosample tracks 102, and then theadjacent magneto-resistive read-sensors 107 immediately read frombiosample tracks 102, which is referred to as a read-after-writeoperation. The magnetic excitation of a molecule by a write-head 107 maybe done with a “spike” or impulse signal. In an alternate embodiment,the write head 107 magnetically excites the molecule with a swept sineor random noise magnetic-excitation and the read head simultaneouslyreads the resonant response of the molecule.

In an exemplary embodiment of the invention, substrate 101 compriseseight biosample tracks 102 corresponding to eight bits in a byte, andhence to eight electromagnetic write-head 107 and magnetoresistiveread-sensor 106 pairs in a typical head-module 105 used in magnetic tapedrive products. However, as alternatives, any number of biosample tracks102 may be used. The number of electromagnetic write-head 107 andmagneto-resistive read-sensor 106 pairs in head-module 105 may be anynumber ranging from a minimum of one to the number of electromagneticwrite-head and magneto-resistive read-sensor pairs in the head-modulesof the tape drives. For example, there are sixteen such electromagneticwrite-head and magneto-resistive read-sensor pairs in a head module ofan IBM 3480™ tape drive. Typically, the number of biosample tracks 102is an integral multiple of the number of write-head 107 and read-sensor106 pairs. In an alternate embodiment, a single device may perform thefunctions of both the write-head 107 and read-sensor 106.

Write-heads 107 may comprise miniature electromagnets, with a coilsandwiched between to poles, such as taught without limitation by U.S.Pat. No. 5,452,164, entitled “Thin Film Magnetic Write-head,” which ishereby incorporated by reference in its entirety. Write-heads 107 maycomprise other structures with similar functionality.

Read-sensors 106 may be anisotropic magneto-resistive (AMR), giantmagneto-resistive (GMR), or tunnel magneto-resistive (TMR) read-sensors,or other devices having similar functionality. AMR read-sensors aretaught without limitation by U.S. Pat. No. 5,005,096, entitled“Magnetoresistive Read Transducer Having Hard Magnetic Shunt Bias,”which is hereby incorporated by reference in its entirety. AMRread-sensors may comprise other structures having similar functionality.GMR read-sensors, which are also known as spin-valve read-sensors, aretaught without limitation by U.S. Pat. No. 5,206,590, entitled“Magnetoresistive Sensor Based On The Spin Valve Effect,” which ishereby incorporated by reference in its entirety. GMR read-sensors maycomprise other structures having similar functionality.

The GMR read-sensors typically have an internal antiparallel pinnedlayer for increased sensitivity, as taught without limitation by U.S.Pat. No. 5,465,185, entitled “Magnetoresistive Spin Valve Sensor WithImproved Pinned Ferromagnetic Layer And Magnetic Recording System UsingThe Sensor,” which is hereby incorporated by reference in its entirety.A recent form of read-sensor, TMR, uses a tunnel barrier layer toaugment the GMR internal structure and to provide increased sensitivity,as taught without limitation by U.S. Pat. No. 5,764,567, entitled“Magnetic Tunnel Junction Device With Nonferromagnetic Interface LayerFor Improved Magnetic Field Response,” which is hereby incorporated byreference in its entirety. TMR read-sensors may comprise otherstructures having similar functionality.

In the exemplary embodiment illustrated in FIG. 1, write-head 107 islonger along the X-axis direction than read-sensor 106. The activesensing portion of read-sensor 106 is smaller than write-head 107, alongthe X-axis, as write-head 107 is used to magnetically excite molecule302 as described with reference to FIG. 3, for identifying the molecule302 by read-sensor 106. If read-sensor 106 were too large in the X-axisdirection, it could potentially encounter non-magnetically excitedmolecules 302 and thus register an undesired false identification ofmolecule 302, as described with reference to FIG. 3.

Head-module 105 may be maintained in linear alignment with biosampletracks 102 along the X-axis by position-error-servo (PES) read-head 108,which reads magnetically encoded servo-alignment marks 104 from servotrack 103 on substrate 101. PES read-head 108 may be, for example, anAMR, GMR, or TMR read-sensor. Magnetically encoded servo alignment marks104 are encoded by the manufacturer of substrate 101 on either a pieceof magnetic tape adhered to substrate 101 or encoded on a magneticrecording layer directly deposited on substrate 101.

In the example illustrated in FIG. 1, particular servo-alignment marks104 shown in servo track 103 are Timing Based Servo (TBS)servo-alignment marks such as those used in IBM's Linear Tape Open (LTO)tape drive products, e.g., IBM tape drive models TS1120™ and TS1210™.TBS servo-alignment marks are taught without limitation by U.S. Pat. No.6,320,719, entitled “Timing Based Servo System for Magnetic TapeSystems,” which is hereby incorporated by reference in its entirety.Servo-alignment marks 104 may comprise other structures with similarfunctionality. The writing of TBS servo-alignment marks 104 in servotrack 103, as shown in FIG. 1, is taught without limitation by U.S. Pat.No. 6,282,051, entitled “Timing Based Servo System for Magnetic TapeSystems,” which is hereby incorporated by reference in its entirety. TBSservo-alignment marks 104 may comprise other structures with similarfunctionality.

FIG. 2 illustrates an exemplary embodiment of servo-alignment marks 104in the form of magnetically-encoded Z-pattern 210 that comprisesservo-alignment marks in servo track 203. Relative to the Y-axis, thedistance between the top and bottom legs of Z-pattern 210 is constantand equal to the sum of line segments AB and BC, which is equal to thesum of line segments A1B1 and B1C1 in path 211. This distance is alsoequal to the sum of line segments A2B2 and B2C2 in path 212, and the sumof line segments A3B3 and B3C3 in path 213. Thus, the velocity of headmodule 105 along the Y-axis relative to substrate 101 may be calculatedby dividing the sum of line segments (AB+BC) by the time to transitZ-pattern 210 by head module 105. This velocity calculation is notaffected by the position of PES read-head 108 along the X-axis, becausethe top and bottom of Z-pattern 210 are both parallel to the X-axis.

The position-error-servo (PES) signal corresponding to the position ofPES read-head 108, and hence write-heads 107 and read-sensors 106, alongthe X-axis may be determined by subtracting the distance AB from thedistance BC each time a Z-pattern 210 is encountered by PES read-head108. As can be seen in FIG. 2, the PES signal from PES read-head 108following path 212 is less than zero because the distance difference(B2C2−A2B2) is less than zero. Similarly, the PES signal from PESread-head 108 following path 211 is greater than zero because thedifference (B1C1−A1B1) is greater than zero. Additionally, the value of(BC−AB) varies linearly as PES read-head 108 moves from left to rightalong the X-axis. Thus the PES signal, as calculated by the differencein distance (BC−AB), provides an X-axis PES signal for head-module 105and its pairs of electromagnetic write-heads 107 and magneto-resistiveread-sensors 106. This PES signal is incorporated into servo controlcircuit 500 shown in FIG. 5.

In an exemplary embodiment of the invention, the value of the linesegment difference (BC−AB) is evaluated based on the time it takes forthe PES read head 108 to cross segments AB and BC when the head-module105 is moving at a constant velocity during its Y-axis seek operation.This is the case where the transit time for the PES read head 108 tocross each Z-pattern 210 is constant. In the exemplary embodiments ofthe invention shown in FIGS. 1 and 2, TBS servo-alignment marks 104 andZ-pattern 210 could be non-magnetic stripes, either lithographed,silk-screened, or ink-jet printed, and read with an optical laser.

In FIG. 2, path 213 is the desired path for PES read-head 108 aselectromagnetic write-heads 107 and magneto-resistive read-sensors 106are aligned with biosample tracks 102. With path 213, the distancedifference (B3C3−A3B3) is equal to zero, i.e., line segment B3C3 isequal to line segment A3B3. For path 211, the distance difference(B1C1−A1B1) is greater than zero, which means that head-module 105 mustbe moved in the +X direction by X-axis actuator 529 of FIG. 5 so thatelectromagnetic write-heads 107 and magneto-resistive read-sensors 106are aligned with biosample tracks 102. The operation of the X-axisactuator 529 is described below with reference to FIG. 5. Similarly, forpath 212, the distance difference (B2C2−A2B2) is less than zero, whichmeans that head-module 105 must be moved in the −X direction by X-axisactuator 529 so that electromagnetic write-heads 107 andmagneto-resistive read-sensors 106 are aligned with biosample tracks102.

FIG. 3 illustrates a side view of an exemplary biosample track relativeto an electromagnetic read-write head for analyzing a biosample. Abiosample track 301 may be deposited on a substrate such as a Peltier™substrate or a magnetic tape media as described in FIGS. 1 and 2. Abiosample 302 may be positioned on the biosample track 301 to beanalyzed by an electromagnetic read-write head 306 in accordance with anembodiment of the invention. Magnetic shield 305 separates write-head303 and read-sensor 304 so that there is no meaningful cross-talkbetween write-head 303 and read-sensor 304 while the electromagneticread-write head module 306 scans along the biosample track 301. The scanmay be performed by moving head-module read-write head module 306linearly in the +Y direction relative to biosample track 301, whichcould equally be done by moving the substrate carrying the biosampletrack 301 linearly in the −Y direction relative to read-writehead-module 306. In an alternate embodiment, write-head 303 andread-sensor 304 may switch positions.

FIG. 4A illustrates a block diagram of a molecule analysis system 400for magnetically exciting molecules 402 in a biosample 302 andidentifying the molecules 402 based on the frequency responses of themagnetically excited molecules, in accordance with an embodiment of theinvention. The molecule analysis system 400 comprises an electromagneticthin-film write-head 403 for magnetically exciting the molecules 402 inthe biosample 302 while the electromagnetic thin-film write-head 403scans biosample track 301.

In one embodiment, the electromagnetic thin-film write-head 403 maymagnetically excite the molecules 402 using a swept-sine signal. Theswept-sine signal is a sine wave with a frequency that increases overtime and may be generated by a signal generator 415. The electromagneticthin-film write-head 403 may magnetically excite the biosample molecules402 using a range of frequencies in order to magnetically excite themolecules 402 with an alternating magnetic field.

In another embodiment, the electromagnetic thin-film write-head 403 maymagnetically excite the molecules 402 using an impulse signal having agenerally narrow square-wave spike that is applied once during themeasurement of the resonant response. Alternatively, the electromagneticthin-film write-head 403 may magnetically excite the biosample molecules402 with an alternating magnetic field that is generated by arandom-noise signal. The random noise signal may be produced by sendinga reverse polarity voltage across a diode.

In another embodiment, the analytical system 400 may further expose themolecules 402 to a direct current (DC) magnetic field while themolecules 402 are being magnetically excited to facilitate themeasurement of the resonant responses from the magnetically excitedmolecules 402. A permanent magnet or an electromagnet may be used toprovide such a DC magnetic field. The DC magnetic field aligns themagnetically excited molecules 402 for improved signal-to-noise ratioduring the alternating magnetic field excitation.

The electromagnetic thin-film write-head 403 may be coated in one ormore protective layers such as a diamond carbon layer 411 to act as anelectrical insulator between the biosample molecules 402 and theelectromagnetic thin-film write-head 403. An outer layer 412, which maybe gold or platinum, covers the diamond carbon layer 411 and thin-filmwrite-head 403 to protect the thin-film write-head 403 from corrosioncaused by the salinity in the biosample 302.

The molecule analysis system 400 further comprises an electromagneticread-sensor 404 for sensing the frequency responses of the magneticallyexcited molecules 402. Molecules 402 are comprised of atoms which arebonded together by ionic or covalent bonds. A mass-spring mechanicalsystem, such as a car and its springs, will resonate at a naturalfrequency which is a function of the square root of the spring rate (inNewtons per meter) divided by the mass (kilograms), and a multiplespring-multiple mass system will have multiple resonances. By analogy,bonds between atoms in molecules provide a spring action and the atomsthemselves possess mass, and thus molecules can have multiple resonanceswhich are a function of the chemical makeup of the molecule. It is theseresonances that are excited by write-head 403.

A target molecule 402 may be held in position during its magnetizationby encapsulating it in a carbon nanotube. As an example, FIG. 4Billustrates an example of a glucose molecule 418 being encapsulated in acarbon nanotube 419. In an alternate example, a target molecule 402 maybe held in place by an antibody, as taught in the commonly-assignedpatent application entitled “Detection Of Analytes ViaNanoparticle-Labeled Substances With Electromagnetic Read-Write Heads”,Ser. No. 12/888,388, herein incorporated by reference in its entirety.In another alternate embodiment, the target molecule 402 is held inposition by surface aligned molecules (SAMs). In yet another alternateembodiment, target molecule 402 is held in a liquid suspension, such asa saline suspension. The resonant response of the antibody, SAMs, andliquid suspension are first gathered without the target molecule 402 sothat the resonant response of the target molecule 402 can be isolatedfrom the surrounding environment.

The electromagnetic read-sensor 404 may be a giant magneto-resistance(GMR) sensor, a tunnel magneto-resistance (TMR) sensor, or ananisotropic magneto-resistance (AMR) sensor. Similarly to the thin-filmwrite-head 403, the electromagnetic read-sensor 404 may be coated in oneor more protective layers such as a diamond carbon layer 414 to act asan electrical insulator between the biosample molecules 402 and theelectromagnetic read-sensor 404. An outer layer 413, which may be goldor platinum, covers the diamond carbon layer 414 and electromagneticread-sensor 404 to protect the electromagnetic read-sensor 404 fromcorrosion caused by the salinity in the biosample 303.

The frequency responses of the magnetically excited biosample molecules402 that are detected by the electromagnetic read-sensor 404 aregenerally small, for example, on the order of 0.1 to 10 microvolts. Themolecule analysis system 400 may comprise an amplifier 416 foramplifying the detected response, which is then further processed byprocessor 410 to identify the molecules 402. For example, a solid-statevoltage amplifier having a gain ranging from 10X to 1000X may be used.

In one embodiment, the processor 410 may compare the amplified frequencyresponses, or a range of responses, of the magnetically excitedbiosample molecules 402 to a table of known frequency responses of agroup of molecules. For example, the sucrose molecule, C12H22O11, willhave different resonances than that of polytetrafluoroethylene, C2F4. Byidentifying the resonances as a function of their frequency andamplitude, the molecule analysis system 400 can identify whether amolecule is sucrose or polytetrafluoroethylene.

In another embodiment, the processor 410 may calculate Bode plots of thefrequency response of a molecule divided by the excitation signal todetect tell-tale resonances. The Bode plots may be calculated bydividing the Fourier transform F(ω) of the amplified frequency response(i.e., the output of the amplifier 416) by the Fourier transform of thesignal from the signal generator 415, in order to normalize the resonantresponse to the magnetic-excitation. Alternatively, processor 410 coulduse power spectrum or Fourier transforms of the output of theelectromagnetic read-sensor 404 to detect tell-tale resonances. Thepower spectrum is the square of the magnitude of the Fourier transformoutput and is calculated by taking the product of the Fourier transformtimes its complex conjugate. The power spectrum is useful because thereis no phase, only amplitude, and thus resonances are readily identified.

The Bode plot is the most useful for detecting the tell-tale resonancesas the output of the electromagnetic read-sensor 404 may be normalizedto the excitation signal to facilitate the identification of tell-taleresonances. Processor 410 may access an internal table 420 of knownresonant responses for different biosample molecules 402 and match themeasured resonant response with the internal table 420 to identify thebiosample molecules 402. The internal table 420 is stored in anonvolatile portion of processor 410 and may include a list of knownmolecules and their resonant frequencies, as well as normalizedamplitudes of those resonant frequencies.

As an example, resonances R1 and R2 may have generally the sameamplitudes but resonance R3 has generally twice the amplitudes ofresonances R1 and R2. The table may include harmonics of these resonantfrequencies, if they exist. For example, resonant frequency R1 has afirst harmonic at frequency 2*R1 and a second harmonic at frequency3*R1, but no additional harmonics of frequency R1 are present. Themolecule analysis system 400 may look up the resonant frequencies,normalized amplitudes, and harmonic frequencies in identifying thechemical composition of a molecule.

In one embodiment, the molecule analysis system 400 may filter out DCsignals from the measured resonant response of the magnetically excitedmolecules 402 to improve the signal-to-noise ratio (SNR) of theresponse. The removal of the unwanted DC signals may be accomplished bybalancing a resistive Wheatstone bridge in which one leg of theWheatstone bridge contains the magneto-resistive sensor. An example ofthe use of a Wheatstone bridge in a molecule resonance sensing circuitis illustrated in FIG. 6.

In another embodiment, the molecule analysis system 400 may furtherfilter out AC noise signals from the measured resonant response of themagnetically excited molecules 402 to improve the signal-to-noise ratio(SNR) of the response, using a filter. AC noises, such as thoseintroduced by lighting and electric power equipment in a laboratory, maybe removed using a band pass filter, band block filter, high-passfilter, Hamming filter, or Butterworth filter, which are known to oneskilled in the art.

FIG. 5 shows an exemplary embodiment of a servo control system 500 forcontrolling the X-axis and Y-axis motion of head-module 520. As anexample, FIG. 5 shows one biosample track 521, and one pair ofwrite-head 522 and read-sensor 523. Processor 524 receivesposition-error-servo (PES) signals from PES read-head 525 when PESread-head 525 reads servo-alignment marks 526 in servo track 527. Basedon this PES information, processor 524 sends a signal to power amplifier528 to control X-axis actuator 529 which in turn controls the motion ofhead module 520 in the X-axis direction. With X-axis actuator 529connected to head-module 520 via mechanical connector 530, head-module520 may be positioned to center write-head 522 and read-sensor 523 onbiosample track 521. Processor 524 may send signals to power amplifier531 to control Y-axis actuator 532 for conducting a scan by head module520 across substrate 533. With Y-axis actuator 532 connected to X-axisactuator 529 via mechanical connector 534, head-module 520 can be movedalong the Y-axis in a controllable manner.

As an example, when a predetermined number of servo-alignment marks 526are read by PES read-head 525, processor 524 stops the Y-axis motion ofhead-module 520. A servo-system for control of X-axis actuator 529 andhead-module 520 along the X-axis direction, particular toservo-alignment marks 526 shown in servo track 527, is taught withoutlimitation by U.S. Pat. No. 5,689,384, entitled “Timing Based ServoSystem for Magnetic Tape System,” which is hereby incorporated byreference in its entirety. The servo-system may comprise otherstructures with similar functionality. As previously described regardingZ-pattern 210, the velocity of head module 520 relative to substrate 533along the Y-axis can be calculated by dividing distance AB+BC by thetime it takes for head module 520 to transit Z-pattern 210. Thisvelocity measurement can be used by processor 524 to control Y-axisactuator 532 to keep head module 520 at a constant Y-axis velocity Vyrelative to substrate 533. The position along the Y-axis of head module520 relative to substrate 533 can be obtained by countingservo-alignment marks 526 or Z-pattern 210 by PES read head 525 andprocessor 524.

FIG. 6 shows an exemplary embodiment of a write and read circuitry 600for writing to a biosample track 621 (i.e., for magnetically excitingmolecules 402) and reading from the biosample track 621 (i.e., forsensing and identifying the magnetically excited molecules 402) onsubstrate 633. Processor 624 may send signals to power amplifier 646which provides power to write-head 647 on head module 620 formagnetically exciting molecules 402 with spike (impulse), swept sine, orrandom noise wave-forms. Processor 624 may further send signals to poweramplifier 645 which powers Wheatstone bridge 640. Read-sensor 623 is onecomponent in Wheatstone bridge 640 and thus receives DC current from theWheatstone bridge 640. Wheatstone bridge 640 serves the function ofbalancing out the zero-magnetism resistance of read-sensor 623 so thatonly the change in resistance of read-sensor 623 is passed ontoamplifier 641. Such resistance change is due to the detection of aresonating 402, which is sent to amplifier 641 and filter 642 beforebeing received by processor 624.

Filter 642 filters out 60 Hz noise, which is pervasive noise in anoffice or laboratory with lighting where processes of the invention aretypically performed. Processor 624 makes the determination of whether amolecule 402 was detected. The change in resistance of read-sensor 623is directly proportional to the magnetic field provided by amagnetically excited molecule 402. As a result, processor 624 couldregister the detection of different molecules 402 during the sensing ofread-sensor 623, depending on different frequencies received by theread-sensor 623. The identification of the various molecules 402simultaneously on the same biosample track 621 may be facilitated by alookup table 644 in processor 624, as described in detail with referenceto FIG. 7. In one exemplary embodiment of the invention, the lookuptable 644 contains a list of different molecules 402, and theirrespective resonance frequencies.

The resonant response table 644 may include a list of known moleculesand radicals such as H+, OH—, C—H, H—C—H and the like, and theirresonant frequencies, as well as normalized amplitudes of those resonantfrequencies. The resonant response table 644 may further includeharmonics of the resonant frequencies, if they exist. The resonantfrequencies, normalized amplitudes, and harmonic frequencies assist inthe identification of the chemical composition of the magneticallyexcited molecules. A matched filter 643 may be present to provide acorrelation between ideal resonances and the measured resonances, andresonances are considered to be detected if the correlation exceeds auser-selectable threshold, such as 80%, where 0% indicates nocorrelation and 100% indicates a perfect correlation. PES read head 625,alignment servo marks 626, and servo track 627 are identical to 525,526, and 527 of FIG. 5, respectively.

FIG. 7 is a flowchart illustrating an exemplary process for identifyinga molecule using an electromagnetic read-write head, in accordance withan embodiment of the invention. The process may be performed by anexcitation-response molecular-identification system, such as system 400,on a biosample as illustrated in FIGS. 1-3. Such an analytical system400 may include appropriate electrical circuits, devices, computerhardware and program instructions to carry out the illustratedoperations. At step 701, an electromagnetic write-head 403 receives analternating AC current and generates an alternating magnetic field whichmagnetically excites a target molecule 402. This magnetization causes anoscillation of the atoms in the molecule 402.

In one embodiment, the alternating magnetic field generated bywrite-head 403 is supplemented by a steady-state, non-oscillatingmagnetic field, which may be supplied by a permanent magnet or anelectromagnet supplied with direct DC current. Such a non-oscillatingmagnetic field tends to align the atoms in the molecule to maximize theexcitation provided by the alternating magnetic field, thus increasingthe signal-to-noise ratio (SNR). In an alternate embodiment, thewrite-head 403 generates the non-oscillating magnetic field that issuperimposed over the alternating magnetic field.

In one embodiment, the excitation provided by the power supply feedingwrite-head 403, and hence the alternating magnetic field generated bywrite-head 403 may be a swept-sine signal. The swept-sine signal is asimple sine wave with a frequency that changes over time and may begenerated by a signal generator 415. Generally the frequency of the sinewave starts at a low frequency and increases with time. Alternatively,the frequency of the sine wave starts at a high frequency and decreaseswith time.

In another embodiment, the alternating magnetic field generated bywrite-head 403 may be a white noise excitation, which is the statisticalequivalent of random noise. An example of white noise is the static onehears on an AM radio. The random noise signal may be generated bysending a reverse polarity voltage across a diode.

In a yet another embodiment, the alternating magnetic field generated bywrite-head 403 may be an impulse signal, which is a narrow square waveof a single magnetic polarity. The square wave is applied only once bythe write-head 403 during a sample period, i.e., during the measurementof the resulting resonant response from the excited molecule 402. Theread-sensor 108 may register the resonant response only after thegeneration of the impulse “spike” wave is completed by write-head 403.

The goal of the swept sine, white noise, and impulse excitations is tocause the molecule 402 to resonate, and it is this resonance which isdetected by read-sensor 404. This resonance may comprise one or morefundamental resonances, and each fundamental resonance may have harmonicresonances which are integer multiples of the fundamental resonance. Forexample, a fundamental resonance of frequency ω1 may have a firstharmonic of frequency 2*ω1, a second harmonic of frequency 3*ω1, a thirdharmonic of frequency 4*ω1, etc.

When the atoms in a molecule 402 are magnetically excited, the molecule402 generates a resonant response that may be detected and measured by amagneto-resistive read-sensor 404 in step 702. The magneto-resistiveread-sensor 404 may be, for example, a GMR sensor, a TMR sensor, or anAMR sensor. The use of these sensors, which are generally used in datastorage tape systems, provides an advantage when using the tape systemsto detect and analyze antigens. In order to facilitate the measurementof the resonant response from the magnetically excited molecule 402, theanalytical system 400 may expose the molecule 402 to a DC magnetic fieldwhile the molecule 402 is being magnetically excited by the alternatingmagnetic field.

Magnetic shield 305, as illustrated in FIG. 3, separates write-head 403and read-sensor 404 so that there is no harmful cross-talk betweenwrite-head 403 and read-sensor 404 during steps 701 (moleculeexcitation) and 702 (resonant response measurement). Read-sensor 404 istypically one leg of a Wheatstone bridge, so that the nominal(zero-excitation) resistance of the read-sensor 404 may be zeroed-out bybalancing the Wheatstone bridge. Accordingly, the output of theWheatstone bridge is only the change in resistance experienced by theread-sensor 404 as it detects the resonances of the target molecule 402.

The resonant response from the magnetically excited molecule 402 thatthe magneto-resistive read-sensor 404 measures is generally too smallfor positively identifying the molecule 402. Thus, an amplifier 641 inthe detection circuit 600 may be employed to amplify the measuredresponse at step 703. Amplifier 641 is typically a solid state amplifierwith predetermined gains of 10×, 100× and 1000×. Such solid stateamplifiers may allow user controlled gain. In addition, the measuredresonant response from the magnetically excited molecule 402 may includea zero-magnetism resistance of read-sensor 623. This DC signal may befiltered out from the resonant response, at step 704, by balancing aresistive Wheatstone bridge in which one leg of the Wheatstone bridge isthe magneto-resistive sensor 404. Such a Wheatstone bridge isillustrated in FIG. 6. The DC signal filtering assures that only changesin resistance of read-sensor 623 are passed to the amplifier 641.

At step 705, a filter 642 in the detection circuit 600 may be employedto eliminate AC background noise, such as 60 Hertz noise emanated bycommon lighting and electric power equipment in a laboratory. Asexamples, the noise filter 642 may be a band pass filter, band blockfilter, high-pass filter, Hamming filter, or Butterworth filter, whichare known to one skilled in the art.

The amplified and filtered resonant response of the magnetically excitedmolecule 402 may be further transformed to a power spectrum at step 706to facilitate the identification of fundamental frequencies and harmonicfrequencies, as follows. First, a Fourier transform F(ω) is created ofthe filtered and amplified output ω of the Wheatstone bridge, of whichread-sensor 404 is a part. Fourier transform F(ω) is in the frequencydomain, and is the frequency representation of the time-domain signalfrom read-sensor 404. Next, the Fourier transform F(ω) is multiplied byits complex conjugate F*(ω) to give the power spectrum φ(ω) perequations (1) and (2). Equation (1) is for an analog Fourier transform,one which is continuous in frequency. Equation (2) is for a digitalFourier transform, which is expressed, for example, in discreteincrements in frequency.

$\begin{matrix}{{\Phi (\omega)} = {{{\frac{1}{\sqrt{2\pi}}{\int_{- \infty}^{\infty}{{f(t)}^{{- {\omega}}\; t}\ {t}}}}}^{2} = \frac{{F(\omega)}F*(\omega)}{2\; \pi}}} & {{Equation}\mspace{14mu} (1)} \\{{\Phi (\omega)} = {{{\frac{1}{\sqrt{2\pi}}{\sum\limits_{n = {- \infty}}^{\infty}\; {f_{n}^{{- {\omega}}\; n}}}}\ }^{2} = \frac{{F(\omega)}F*(\omega)}{2\; \pi}}} & {{Equation}\mspace{14mu} (2)}\end{matrix}$

The resonances and harmonic frequencies are peaks in the power spectrumφ(ω) and may be identified by peak-detect algorithms, as known in theart, such as used in recording technology such as for tape drives. Theresonances and harmonic frequencies detected by the read-sensor arecompared to a table of known resonant responses for known chemicalradicals, such as H+, OH—, C—H, H—C—H, etc. From this table, and theaforementioned resonances and harmonic frequencies, the chemicalcomposition the target molecule 402 is identified, at step 707. Once themolecule 402 is identified, the analytical system 400 may present theresults of the molecule scan to a physician or clinician at step 708,for example, by informing the physician or clinician of the presence orabsence of target molecules in the biological sample.

Referring again to FIG. 1, there may be multiple target molecules in thebiosample tracks 180 that the excitation-response process describedabove may identify. If there are more biosample tracks 180 thanwrite-head 106 and read-sensor 108 pairs in head-module 104, head-module104 may scan the biosample tracks 180 in a serpentine pattern. Thehead-module 104 performs a scan in the +Y direction, as head-module 104only provides read-after-write capability in the +Y direction asillustrated in FIG. 1. Then a second head-module comprising a mirrorimage of head-module 104 may perform a read-after-write operation in the−Y direction. In one embodiment, during the excitation-response process,the write-head 106 and read-sensor 108 pairs are stationary and physicalmotion along the +/−Y direction only occurs in moving from one samplesite to the next. The use of IBM's Timing Based Servo, as read by aservo read-head on head module 104, may assist in the guiding ofwrite-head 106 and read-sensor 108 from one target molecule to the next.

To facilitate the detection of different target molecules, calibrationof read-sensor 108 may be performed. An exemplary read-sensorcalibration process is described, for example, in the commonly-assignedpatent application entitled “A Circuit For Detecting Analytes ViaNanoparticle-labeled Substances With Electromagnetic Read-Write Heads”,Ser. No. 12/888,408, herein incorporated by reference in its entirety.The calibration process may use of a variety of known moleculespositioned in known locations in biosample tracks 180, where theresonant responses of these molecules are known. Variants of knownmolecules are formed of atoms of carbon isotopes. For example, Carbon-12is replaced by Carbon-13 or Carbon-14. This affects the resonances ofthe known molecule, causing a shift in the resonant frequencies, becauseof the change of mass of the atoms. magnetically excited nanoparticlesof known magnetic intensity may be used in fixed positions alongbiosample track 180 to “label” the known molecules used for calibrationpurposes. These nanoparticle labels would typically be of a highcoercivity, such as Barium Ferrite, so that the magnetization of thesenanoparticles is not affected by write-head 106 during theexcitation-response molecular-identification process.

While the exemplary embodiments of the invention have been illustratedand described in detail, it should be apparent that modifications andadaptations to those embodiments may occur to one skilled in the artwithout departing from the scope of the invention. Aspects of thepresent disclosure may be embodied as a method, system or computerprogram product, and may take the form of an entirely hardwareembodiment, an entirely software embodiment (including firmware,resident software, micro-code, etc.) or an embodiment combining softwareand hardware aspects that may all generally be referred to herein as a“circuit,” “module” or “system.” Furthermore, aspects of the presentdisclosure may take the form of a computer program product embodied inone or more computer readable medium(s) having computer readable programcode embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN), awide area network (WAN), Ethernet, or the connection may be made to anexternal computer, for example, through the Internet using an InternetService Provider.

Aspects of the present disclosure are described above with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of thedisclosure. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures described aboveillustrate the architecture, functionality, and operation of possibleimplementations of systems, methods and computer program productsaccording to various embodiments of the present disclosure. In thisregard, each block in the flowchart or block diagrams may represent amodule, segment, or portion of code, which comprises one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

What is claimed is:
 1. An apparatus for identifying a molecule,comprising: a head module comprising: an electromagnetic write-headconfigured to magnetically excite the molecule to be identified with analternating magnetic field, and a magneto-resistive read sensor formeasuring a resonant response of the magnetically excited molecule to beidentified; and a processor coupled to the magneto-resistive sensor, theprocessor being configured to compare the resonant response to a tableof known resonant responses to identify a chemical composition of themolecule to be identified.
 2. The apparatus as recited in claim 1, thehead module comprising a magnetic shield separating the electromagneticwrite head from the magneto-resistive read sensor so as to prevent anymeaningful cross-talk between the electromagnetic write head from themagneto-resistive read sensor while the electromagnetic write-headmagnetically excites the molecule to be identified.
 3. The apparatus asrecited in claim 1, comprising a filter coupled to the processor andconfigured to filter 60 Hz noise.
 4. The apparatus as recited in claim1, comprising a servo control system configured to: determine whetherone or more of the electromagnetic write head and the magneto-resistiveread sensor are aligned with the molecule to be identified; and alignone or more of the electromagnetic write head and the magneto-resistiveread sensor with the molecule to be identified.
 5. The apparatus asrecited in claim 4, the servo control system comprising: a first poweramplifier configured to cause a X-axis actuator to control motion of thehead module along a first axis; a second power amplifier configured tocause a Y-axis actuator to control motion of the head module along asecond axis perpendicular to the first axis; a position error servo(PES) read-head configured to generate PES error signals based onreading one or more servo-alignment marks in proximity to the moleculeto be identified; and a processor configured to: receive the PES errorsignals from the PES read-head; and send one or more signals to one ormore of the first power amplifier and the second power amplifier tocontrol motion of the head module.
 6. The apparatus as recited in claim1, wherein the electromagnetic write head is a thin-film write head. 7.The apparatus as recited in claim 6, comprising: a protective layerdisposed on a surface of the thin-film write head; and an outer layerdisposed on the protective layer.
 8. The apparatus as recited in claim7, wherein the protective layer comprises diamond-like carbon; andwherein the outer layer comprises one or more of platinum and gold. 9.The apparatus as recited in claim 1, comprising: a protective layerdisposed on a surface of the magneto-resistive read sensor; and an outerlayer disposed on the protective layer.
 10. The apparatus as recited inclaim 9, wherein the protective layer comprises diamond-like carbon; andwherein the outer layer comprises one or more of platinum and gold. 11.The apparatus as recited in claim 1, wherein the molecule to beidentified is disposed one of a plurality of a biosample tracks of abiosample substrate.
 12. The apparatus as recited in claim 11, whereinthe biosample substrate comprises, or is coupled to, a plurality ofservo-alignment marks; and wherein the plurality of servo-alignmentmarks are configured to facilitate alignment of the electromagneticwrite-head with the biosample tracks of the biosample substrate.
 13. Theapparatus as recited in claim 12, wherein the plurality ofservo-alignment marks are non-magnetically encoded on the biosamplesubstrate.
 14. The apparatus as recited in claim 12, wherein theplurality of servo-alignment marks are magnetically encoded on thebiosample substrate.
 15. The apparatus as recited in claim 14, whereinthe plurality of servo-alignment marks are magnetically encoded on thebiosample substrate in a form of a magnetically-encoded Z pattern. 16.The apparatus as recited in claim 12, wherein the plurality ofservo-alignment marks comprise Timing Based Servo (TBS) servo-alignmentmarks.
 17. The apparatus as recited in claim 12, wherein the pluralityof servo-alignment marks are encoded on a magnetic recording layerdeposited on the biosample substrate.
 18. The apparatus as recited inclaim 12, wherein the plurality of servo-alignment marks are encoded ona piece of magnetic tape adhered to the biosample substrate.
 19. Theapparatus as recited in claim 11, wherein the biosample substratecomprises a Peltier substrate.
 20. The apparatus as recited in claim 11,wherein the biosample substrate comprises a magnetic tape medium.